30 DAY ON ENTRY VISA?

30 day on entry visa? Except it isn't a visa.The need for a visa is waived for many nationalities   (https://www.speedy-visa.com/visa-exempt-countries) upon arrival if you didn't get a visa before traveling and immigration gives you a 30 day permission to stay in Thailand without the need for a visa.During the last week of your 30 day stay, you can go to an immigration office and get a 30 day extension of your permission to stay. You're not extending a visa. You never got a visa. You're extending  your permission to remain in Thailand.Even if you go into immigration several days before your first permission to stay expires, the new 30 days is added to the first 30 days, so you don't lose any days by going in early.