Honestly if he doesn't stop removing his clothes when inappropriate then you need to be very stern with him and tell him he must keep his clothes on when people are around.
I know it may seem or be cute to you when he takes off his clothes and runs around naked. But you must not encourage it by mentioning how cute he is and stuff.
When he takes off his clothes, don't laugh as he then knows you know it's funny then it becomes a game for him.
When he takes his clothes off you tell him to put them back on and don't smile no matter how hard it is too not smile.
If he doesn't put his clothes back on then you put them back on him and tell him if he removes them again he'll get a spanking.
If he takes the clothes off again then spank him like you said you would or put him in time out.