I am in Thailand, due to fly back to canada tomorrow, what can I do to treat seroma?

Unfortunately you may have a persistent seroma for some time. It may recur following your next aspiration. I would use your compression garment ( check with your surgeon first). If you can not get to a Plastic surgeon in Canada you can go to your local emergency department and they could organise an ultrasound guided aspiration of the seroma. Ensure you stay well hydrated and mobilise on the plane to reduce your risk of a DVT. You should also check with your surgeon if he would like you to take any DVT prophylaxis prior to flying. (after an abdominoplasty). 

The seroma could still comeback even after a 3rd aspiration. That is not unusual! Ask your surgeon if he is okay with you wearing a compression garment. If you get a seroma again after you get back to Canada, then find a local plastic surgeon and see if they can drain it for you. Good luck and i wish you a speedy recovery