Should I use Kayak, Priceline, Cheapflights, just watch the price on Google flights? What is the best way to find affordable flights to Thailand?

Hey everyone. After some advice. Nz passport arriving in Bangkok June 6th from Phillipines and assuming we can get 30 day visa on arrival. We would like to stay 60 days. Can we book exit flight for 60 days later??? Or do we need a flight out within 30 days. I have read some people buy a refundable flight... which website does refundable flights??? Thanks to anyone who can help.....

Hello, Please I need help, " First I'm sorry about my Language I hope you Guys understand me " I want to flight to Thailand But I'm wondering Do i Need to book a return flight Ticket back to my country or I only book another Ticket from thailand to Laos for example!

Thank you in advance!!