@Abigail *****
A lot of things are bad about the STV:
1. To get a 90 day extension of stay, you need a pre-booked, pre-paid hotel room with the owner's tax ID number, OR proof that you own a condo, OR a rental agreement.
2. You'll also need the original insurance documents for the length of time. I seen rejections where someone entered in Thailand for insurance that's good for 90 days, then they renewed the insurance, and the immigration office rejected the extension of stay.
3. You can not convert the STV to any other type of extension of stay.
4. It's unknown what will happen after September 30, the last valid date for the extension of stay for the STV; will a person be able to stay longer? Will they not be able to stay longer? We don't know..
5. It's unknown what would happen if you enter Thailand after July 3; would you only be stamped up to September 30th?