can I use Apple Watch with straight talk?

If you have Straight Talk as a phone provider, then yes, you can connect your watch and use it as long as you carry your phone with you at all times. Unfortunately, the watch will not work independently, as Straight Talk is not a provided carrier.

Apple Watch Cellular will not work on Straight Talk.

See this document for supported carriers: Apple Watch - Carriers - Apple

(You can use the Apple Watch Cellular if your carrier is Straight Talk, but it will NOT have cellular service.)

Only if Straight Talk supports Watch, ask them.