Ok, so you came back a month ago as stated and you had a girlfriend for 2 weeks, so that is 6 weeks since you have been back right.....please read on.
Am I missing something or is this a dead give away, in other words how does she know the sex of the child, as the earliest you can find out what sex the child is, is 14 weeks through an ultrasound, however most Dr's recommend a scheduled ultrasound between 18-21 weeks and it's still not 100% accurate.
Now if my math is correct you would have been with her 2 weeks after you returned here for a month, meaning the kid is not yours, why, because she said it was a he and she can't know that unless it's someone else's because 14 weeks haven't passed to be able to determine the sex of the child.
Genius, yes I know, sounds like another scam to me.
EDIT: Having read the other posts and your replies to some of them, I note that you said you made a mistake when you said she said it was a he, that said, life as a single father is tough, very tough, been there, done that.
What solution do you have, stay a single dad and father your two daughters or confirm that the child with this beauty is actually yours and then decide how it's going to work out.
The only way I can see it working out is she moves in and becomes mum to all 3 kids while dad works his ringer off, at least that way, you will have some time to yourself, I mean, after all, how much is an extra mouth and bit cost to feed in Thailand.
Wouldn't be talking wedding bells until you see how the move with her is and how your daughters adjust to their new mum, at least that way, if you don't like what you see, you give her the marching orders and she takes the kid, that or you think about jumping off the balcony.
Good luck & buy a lottery, just for luck ????