Please advise what is a good way to stop thumbsucking?

See Orthodontist: If you are asking with regard to a child, then you can see an orthodontist about an appliance called an orthodontic thumb rake. It's a dental appliance that is placed in the child's mouth - similar to braces - and it gently pokes your child's thumb every time he/she tries to suck on their thumb. It is very effective in stopping the habit.