There is not much difference. The progressive form could indicate ongoing or past activity.
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Is there any difference between saying 'thanks for your help' and 'thank you for helping ....' and does '' thank you for helping...'' show or imply past activity ?
It could also indicate the future.
"I can't wait to meet you next Tuesday when you assist me with running the charity stall at the animal welfare event. Thank you so much for helping".
The event hasn't happened yet and the person has only agreed/offered to help but we would still use the present continuous.
Remember - if you don't use correct capitalisation, punctuation and spacing, anything you write will be incorrect.