TG or SQ FFP?
 

Overall, which airline has a better FFP?

Out of those two, I'd say TG.

Same mile earning ratios as SQ, but you get a free upgrade if you're gold, plus reduced mileage/free upgrade around your birthday (which SQ doesn't offer).

I looked through the award charts for both airlines
A business class award ticket for BKK-LAX on TG requires 140000miles
but the Star Alliance awards for SQ from BKK-LAX requires only 120000miles
How come it's like this?

TG wins flat out.

SQ FFP is only for those that want short term redemption on Sq's 77W and A380 flights. and even so, the A380 F is not for redemption by any award redemption atm.

They are both terrible. All Asian carriers have horrible frequent flier programs.

If you fly in paid C or F, join LH or BD.

If you fly in Y, join UA.

Seriously.

That's why I joined BD once TG wouldn't let me re-qualify for gold. Paid C, minimum 200% miles (more the higher tier you are), 300% for F. TG/SQ suck - 125% miles C, 150% miles F. Come on.

It's never this easy.

* SQ gives tier bonus miles for silver/gold pax. TG doesn't.
* TG's awards require more miles than SQ's.
* On top of that, you get a discount of 15% for any SQ awards booked online.

The OP also doesn't state where they're based -- for me, the fact that I can put my credit card miles into a KF account, but not a ROP account, alone tips the ball into SQ's court.

If I join BD's FFP how do I contact the office?
Neither Bangkok nor LA have a bmi office

I am pretty sure you can just sign-up on-line.

When I need to call them, which to date has only been for award bookings, I use Skype.

Once you are a Gold, in the subsequent years, once you hit I believe it's 57,000 status miles, your earnings double. For each mile in F, except on SQ, I earn 6.25 redeemable miles. Sweet.

Bangkok has a BMI office. Now, I don't know building names, but you go down Silom Road (heading west) until the corner of the cross street where the skytrain bends towards Chong Nonsi BTS (it could be Narathiwas Rd).

On the corner diagonally opposite TG's customer service office (still under renovation?) i.e. the side closer to the BTS station Sala Daeng, there is an office building.

In that building is a BMI office. I can remember reading on a post a while back that someone in Diamond Club was helpfully assisted by this office. ^