I think you'd better be good and do what Brother Hung tells you.
6 seconds sound clip from the Executioners From Shaolin (1977) movie soundboard.
You can hear this line at 00:24:06 in the DVD version of the movie.
Quote context
[...]
- Yeah, Brother Hung, he wouldn't mind at all, huh?
- Hey, I'm in a good mood. But if you don't stop...
- Brother, do you remember the first time we met her?
- This young lady said that our red boat kung fu, was really nothing special.
- Well, no matter what, when you both go off to bed this evening,
- I think you'd better be good and do what Brother Hung tells you.
- You keep your legs together, and tonight, he'll be begging you! And then...
- Brother, I'm just joking. What does it matter, huh?
[...]