Hi I'm Filipina as well. you can go to immigration for 30days visa extension and pay 1900baht. you can apply before your visa expires. I applied one month before ma expire yung current visa ko nun.
My suggestion when you arrive in the Philippines, do not buy a simcard right away from the airport it's so expensive. you can buy from any convenient store from the airport or any store outside the airport. or get E-sim
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if you will buy simcard outside airport the price might be around 50php and with free 1gb data. if you need to load up your sim you just need to go any
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convenient store near you, load up online just register to specific network provider app and explore the app for more info.