Hi! I'm applying to go and study in a shaolin martial arts school in China for a month,

so a 30 day visa wouldn't be enough (and a 2 month one is not possible). The school have told me to apply for a 45 day visa, I haven't heard of one before, do you know if I can get this visa in Phnom Penh? I will also have a normal invitation form from the school.
Thanks!
Lola