Inform your tenant saying the unpaid electrical bills will deduct from the deposit.

Should have let them connect electricity under their name. Anyway if under your name you can ask TNB to cut power anytime, right?

Why dont u just whatsapp them and screenshot the unpaid bill?

Sometimes they forget. Sometimes they too busy.

Also be mindful to msg them with a casual hey bro i notice u havent pay the tnb bill yet. Dont forget to pay and forward the receipt to me once done ya.

Just treat them with respect. Im sure they would pay it once rhey receive the msg

Tell and remind him to pay or risk eviction, deposit are never meant to be deducted, as it's your final trump card as collateral.
Later deducted, he move out you also another headache

You are wrong, TNB will still black list the unit until full payment when they can't find the tenant.