Like nearly everywhere,  sightseeing is expensive and Thailand is no exception.  But there is a way to save a nice amount of money in Thailand for many things you need.  Tourist attractions,  ferries and much more.

While many touristic attractions cost around 500 Baht (12 Eur)  for foreigners,  they are a lot cheaper for Thai people,  mostly its 1\3 of the price.  Now you aren’t Thai, obviously –  but there is a way around that.
An official, aknowledged and for such purposes accepted document,  is a Thai driving license.  When you have one,  you pay less,  thats what expats told us.
Its a bit of a challenge to get one as there is quite some paperwork and preparation involved.  Thailand has a nice amount of burocrazy and stamps in many colors ,  but its not steep, at last.

The driving license is aknowledged and is the document you need to get the Thai price for things.
So if you plan an extended stay in Thailand or use it as your homebase around South East Asia,  it might be well worth a try to get one.