Do I need to cancel my previous visa before doing a border bounce for a 45-day visa?

There's no such thing as 45 days visa on arrival. Visa on Arrival is 30 days.

You are probably talking about the 45 days visa exempt.

If you're on the original 90 day non-B visa sticker in your passport or evisa, then you cannot cancel a visa.

If you're on a 1 year extension of stay you applied for from an immigration office, then you have to cancel this before you are leaving as part of the terms you agreed to when you applied for it.

You would take a letter from your work saying when your last day is along with your cancelled work permit to immigration and they will cancel your extension for that day.