@Colin *****
there is no 3-months Tourist Visa.
If you mean the 60-days Tourist visa, which can be extended on Immigration ONCE for 30 more days, summing up to 90 days stay, then you should note the following advice:
The 60 Days tourist visa is a “SINGLE ENTRY” category tourist visa.
This means you can only enter Thailand ONE TIME and receive 60 says “stay permit”
Theoretically, you could buy a re-entry permit for 1000.- Baht, which would keep your 60 days stay permit alive, if you left Thailand and re-enter during the period of these 60 days.
The question is, will this make sense or not? Will it be fit to your travel plans?
You can stay the first 60 days, then leave Thailand, have a holiday in a neighbouring country and re-enter “visa-exempt”. This will give you 30 days stay permit, which you can extend on Immigration for 1900.- THB for 30 more days.
After this your options are limited, theoretically you can add one more 30 days “visa-exempt” entry by doing a ”border run”