With my very basic understanding, it is something like nagtatayo ka / umuupo ka. These would be strong commands, so you could add 'na' to soften the imperative, giving you something like 'you, sit already' I'm interested to see some other answers, but I imagine you can make these pronounless commands. Nagtatayo na / umuupo na

Stand up - Tayo! Sitdown - Upo! You can just use the root word

Here's how to say "Stand up" and "Sit down" in both formal and informal forms. Formal: Stand up = Tumayo ho muna kayo. (Tumayo po kayo.) Sit down = Maupo ho muna kayo. (Maupo po kayo.) Informal: Stand up = Tumayo ka. Sit down = Maupo ka.

stand up: Tumayo po kayo (formal) Tumayo ka (formal) Tayo. (colloquial) sit down: Maupo po kayo (formal) Maupo ka (informal) Upo. Colloquial)