If you want to stay longer than 30 days, you need a visa. If you go there on land, you can only stay 14 days without visa. Holder of student visa is entitled to stay in Thailand for a maximum period of 90 days. He or she may apply for an extension of stay at the Office of the Immigration Bureau and may be granted such extension for a period of one year from the date of first entry into Thailand.
All of the travelers should take Measles-mumps-rubella (MMR) vaccine, diphtheria-tetanus-pertussis vaccine, varicella vaccine, polio vaccine, and your yearly flu shot. Most travelers also take Hepatitis A and Typhoid. Some vaccinations differ per country, so it is always good to do research about what vaccinations you should take.
Thailand is a cheap country in general. For example, the price of the street food is very cheap. You can sometime get a full meal with just €1. And also, the transportation is very cheap.
It would be much helpful to do research about the country. That way, you would be easier to understand Thai people and the culture in general. It is also important to do a research about the prices because they will sometimes try to let you pay more than necessary.