hostel travellers are a certain breed that love the atmosphere of living with new strangers everywhere they go. It's super social and easy to make friends.
I despise hostels, but have friends who love them 😅
You can just email a hotel directly and book through them. The time it takes to get the test results back doesn't depend on an agency or who you paid how much. It's up to the hotel to send the test to the hospital and then for the hospital to send the results back, at which point the hotel staff should tell you your results.
You can read people's reviews of each hotel (on Google maps or the SHA+ hotel website) and see how long it took them to get their results back.
in what case? What situation are you in? What passport do you have? What visa? Have you used the cow extension?
There are hundreds of different factors for people coming into Thailand and you shared literally no information about your situation, except that they let you in.
The goal of immigration is not to do immigration related work, it is to slowly but effectively reduce the amount of trees in the world, one paper sheet at a time. Also, to waste as much of everyone's time as humanly possible.
I know this group is here to help and all questions should be welcome, but why are you asking a bunch of strangers online a question that only your hotel can answer...?