I use agoda app prices are actually cheaper on that app and I've used it for buying six Thai air asia flights in the last 4 months no problems and the Agoda app remembers my passport details
Luma Asian Pass Travel Health Insurance can be purchased at any time during your travel. It does not have to be purchased at your home country. You will receive an email with your policy within minutes of purchase. They have weekly, monthly, all the way up to 8 months premiums. Some well meaning people hand out misinformation often