Q: Can I backtrack?
A: You can backtrack within countries and continents, but you cannot re-enter a continent after leaving it, except: (a) a transit without stopover in Asia on a flight between Europe and SWP or vice versa, (b) a transit without stopover in Asia on a flight between North America and SWP or vice versa, (c) a transit without stopover in North America on a flight between South America and SWP, Asia or Europe or vice versa, (d) a transit without stopover in Europe on a flight between Europe and Ghana or Nigeria or vice versa. Any of these transit without stopover benefits can be taken in either direction (eg. Europe-SWP or SWP-Europe) and either before or after you wish to enter the continent for the second time to use your stopovers there. You can only leave and re-enter the continent of origin once, except for North America where you may have an additional transit without stopover.

Only one intercontinental departure and one intercontinental arrival permitted in each continent.
Exceptions: Two permitted in North America. when one is a transfer without stopover.
Two permitted in Asia when one is a transfer without stopover or on direct single plane service between the Southwest Pacific
And Europe.

Ok, Can someone help me with this. I'm confused.

I'm trying to book DONE4 Originating from BKK
MY first leg is BKK-SYD
My second leg is SYD-LHR with transit in either bkk, hkg or sin.
I called the AA RTW desk and they said that I was unable to do this.
Can someone confirm???

Much appreciated.

then where are you going,
so you want to go asia- australia- europe-???

correct.
would be something like this

bkk-syd
syd-lhr
lhr-jfk

If you 'touch' a continent, even in transit you are deemed to have entered it.

As Asia is your continent of origin, you can only re-enter it once. If you wanted to go through to LHR, then NA then back to Asia, you cannot within the rules as your transit on the way to LHR would have been your re-entry to Asia.

If you need to originate in Asia, the 'SWP-Europe Transfer without stopever in Asia' clause cannot apply.

Also, you cannot re-enter your originating continent until you have traversed both the Pacific and Atlantic oceans.

So the following may be valid as you are not originating in asia:
jfk-bkk-syd-lhr-jfk

Further to Serfty's post, your options to continue to LHR would be as follows:

BKK-SYD-JNB-LHR (making it a minimum xONE5 fare)
BKK-SYD-LAX-LHR (going eastbound RTW)

So, (having already visited Asia), is it OK to do SYD-SIN-LHR, but changing flights in SIN (i.e. with a 2 hour connect time)? Or does it have to be SYD-LHR on the same flight? I'm not concerned about using an extra segment (that's the point actually - it's more tier points this way I believe!)

It'll have to be a "same plane through service". That limits it to QF or BA. CX through HKG change flight numbers. You can't transfer to another QF plane in SIN because you'd change flight numbers.

The following is from CX (some time ago, but I think it is still valid)
Only one intercontinental departure and one intercontinental arrival is permitted in each continent...
Exception 1....
Exception 2 - Two intercontinental departures and arrivals are permitted in Asia, when one is transfer without stopover or on direct single plane service, between the Southwest Pacific and Europe.

This indicates a transfer is allowed.

Not quite, the rule says you cannot reenter your country of origin, not your continent and, yes, there's also a separate rule about not reentering continents, but that rule has exceptions and Asia is one of them. So, in short, I'm not that clear that what the OP wants is against the rules.

Actually, the AA RTW desk is correct in denying you this routing because of the rule "You can only leave and re-enter the continent of origin once". If you were originating in another continent (e.g.NA) and then continuing with BKK-SYD-LHR then the routing would be valid.

My reading of the rules would allow the OP's itinerary, though I'd agree that the rules might be somewhat ambiguous.

There appear to be 3 relevant rules here (all in the "Routing" section), 2 of which have exceptions:

Rule 3 seems to clearly allow 2 intercontinental arrivals and departures from Asia, and long as 1 of them is a transit between SWP and Europe. I can find nothing in the rules in which the application of this rule makes any distinction based on continent of origin. However, Rule 4 eliminates the possibility of originating in BKK and then traveling from Australia to Europe via BKK -- the transit point would need to be HKG or SIN.

Rule 5 is where it becomes interesting, as it states that a SYD-(SIN)-LHR trip would be 3 continents. So, does that mean that if you've already been to Asia once, you'd need to count your transit through Asia as another continent (that is, count Asia twice as a continent)? While the wording of the rules might be a bit ambiguous, it seems clear to me that the intent of the Exception to Rule 3 serves 2 purposes: it allows the 2 arrivals/departures from Asia, and it means that Asia is counted only once as a continent, whether or not you take advantage of the exception.

So, my suggestion to the OP is to re-call the AA RTW desk and find an agent who will read the rules more along the lines suggested here.

I beg to differ. There is no such rule.

Thanks for all the info guys. I called the AA RTW desk AGAIN. and this time I got a different answer.
Essentially I want to start in BBK so my schedule will be as follows
BKK-SYD (on QF2)
SYD-LHR (either on BA10, QF1, QF29, or QF31 - all same plane through service but transit in Asia, either Bkk, Sin or Hkg)
LHR-JFK (on AA131 - TransAtlantic)
** Various segments in US**
JFK-BKK (CX - TransPacific) end...

The guy I spoke to at AA RTW said that SYD-LHR with transit in Asia is do-able.... but the woman I spoke to earlier said it was not. So now I'm even more confused...

Why are you confused? The previous agent got it wrong (happens all the time), the RTW desk got it right (happens most of the time). Forget the wrong answer and go with the good one, which agrees with what you want. You should be happy, not confused.

lol. No i was confused with who was right...
So as long as I do not transit in BKK then I'm fine then.

Thanks..!!!