I'm going to be traveling in Asia for several months. I usually fly out of lax on Eva direct to taipei one way and have never been asked for a return ticket. This time I made the mistake of booking a two leg trip through Expedia which goes on Alaska to SEA and from SEA to TPE on EVA.

Alaska said they could not check the in unless I had a ticket showing I was leaving aipei within 90 days. I requested to sign a waiver removing them from liability if I was turned away by immigration in taipei but they said they didn't do that. So I booked a ticket from TPE to Bangkok.

They then told me I needed a return ticket to the US. this has never happened to me on any airline before. I have booked onward tickets when in this situation before with no issue but Alaska would not budge. insisted they would only accept a return ticket to the US.

So now I have also booked a return ticket to LAX for a date when I don't plan to return. They warned me not to cancel the ticket saying they will be checking and IF I cancel I'll get a huge fine. The thing is I really need to cancel it because it will be a huge waste of money if I don't.

Can anyone verify this is true and exactly how long are they checking to see if I have cancelled my ticket?

Could I safely cancel it after checking in for the second leg of my trip in SEA?

Expedia gives me 24 hours to cancel and I assume they are not still going to be checking my ticket after I arrive in taipei in ordee to fine me as claimed.. But the problem is by the time I arrive in taipei I think 24 hours may already have elapsed and it will be too late to cancel. So it seems like my best chance would be in SEA after checking in with EVA.

what is my best option in this situation?

I cannot answer your question, but I'm really curious how Alaska deals with people who are relocating to Taiwan (for work, school, or retirement).

You might see if you can get free access to Timatic to determine what requirements Taiwan has for onward and/or return tickets for visitors. Timatic is what the airlines rely on to determine whether passengers meet immigration requirements at a destination airport. It looks like UA provides free public access to Timatic here:

https://www.united.com/en/us/travel/...l-requirements

Did Alaska happen to mention who, exactly, is going to find you if you cancel the return ticket it forced you to buy? If this is just a scare tactic that the Alaska agent used to get you to buy another ticket, then a complaint to the U.S. DOT would be in order.

By the way, are you certain that you were actually talking with Alaska, and not a scam travel agency?

Just book an onward ticket using miles from an FFP that offers free cancellation/redeposit.

I was at the check in counter for the airline so it was definitely alaska. The lady at the counter also called in to customer service and consulted her supervisor. All said this was the airline policy and would not budge. To be honest I'm not entirely sure they knew what was what, they had clearly never encountered such a situation before - nevertheless I was forced to buy the ticket to board.

They did not mention who would fine me - I got the impression alaska themselves? But I do think it could very well have been a scare tactic. The lady at the counter I had to deal with was extremely rude and seemed to enjoy being short with people

I haven't checked, but I'm pretty sure that the U.S. DOT would not allow an airline to "fine" someone who cancelled a ticket within the permissible 24-hours-after-purchase full-refund period.

Should you ever encounter such a situation again, I would pull up the Timatic rules on a smartphone and show the rules to the agent.

See also:
Anyone got asked about onward flight when traveling to HKG? (I did, once recently)

Airlines all over the world are responsible for ensuring compliance with country specific entry requirements. I fail to see why anyone is shocked when they request proof.

Yes, but the OP's complaint in this case is somewhat different:

"I have booked onward tickets when in this situation before with no issue but Alaska would not budge. insisted they would only accept a return ticket to the US."

(Emphasis added.)

Ah. I missed that part, and would have certainly been annoyed if an airline tried to force me to jump through that hoop.