Just say politely you don't need their help now and you will ask them if you're interested in training service, I'm sure they'll understand

The OP starts a thread and just disappears. Yet another troll?

Update:

Thanks to the responses here it's clear that I overestimated the "saving face" aspect of this situation. I'm new and almost everything I've read or heard about Thailand stressed how serious it is so I wanted to act conservatively. At home it wouldn't have been an issue because I know the social rules.

I walk into the gym feeling totally relaxed; of course this is going to be easy.

I talked to both the trainer and the manager and they more persistent than ever. I had to use almost everything mentioned in this thread to convince them that I didn't want training. It was all friendly of course, however they really didn't want me to say "thanks, but no thanks".

Now everything is back to normal.

Cheers