Incorrect. It's called a Single Entry Tourist Visa. The 30 days 'extention of stay' has to be applied for in Thailand and, although rarely refused, is NOT a given.
The single entry tourist visa is valid to USE once to enter Thailand for 60 days. It doesn't allow you to renew that visa for a further 30 days, you have to apply for an extention of stay and each application is granted at the discretion of the Immigration Office where you apply. Technically it is a 90 days visa but only because it has to be used within 90 days from it's issue date.
The visa you applied for is valid to use for 90 days from it's date of issue, it only gives you a 60 days stay in Thailand. Unfortunately you obviously misunderstood the terms of the visa. The anger you feel should be directed at yourself not the evisa website via Belgium!
Technically it's your girlfriend's landlord or your girlfriend(using the owners details) who is required to file the TM30 if you stay in her "rented condo"
Technically you need 20k baht in cash or currency equivalent, proof of onward travel within your visa/exemption and an address where you're staying, however these are rarely asked for at Immigration