If you mean to apply for a visa before you visit Thailand, like the retirement visa as in application for a new Non Immigrant O or O-A or O-X visa, please look at the requirement of the Thai Embassy in the country where you apply.
I hope you can understand that we can not tell what an unknown Immigration Officer at an unknow immigration booth at an unknown international airport in Thailand on an unknown date will do. For sure we can tell he will do his job, if that is with or without asking a question is his/her personal decision.
IF you got an Admitted to stay period of 30 days it is called an Visa Exempt Entry, NOT a Visa on Arrival which some countries need to buy for 2.000 Thb and only give 15 days of stay.
Yes, if you re-enter by land you get a new 30 day Visa Exempt Entry but can only do this twice a calendar year.