There are two fortnightly Drink and Draw sessions in Phnom Penh currently, conveniently running on alternate weeks, offering two hours with a life model for $3.
At ShowBox, #11, St 330, every other Sunday. 7.30 pm start. BYO materials.
At Cloud #32, St 9, every other Monday. 7.30 pm. Additional drawing class at 7 pm for an extra $1.