Correction to the advice above;

Star Gold indeed does entitle an extra 20kg,
Star silver does not entitle any extra baggage. See here: http://www.staralliance.com/en/trave...er_status.html

Being THAI ROP silver, gets an extra 10 kg, but only on THAI flights. UA status won't help.

Premier Associate is = to Star Silver Status, but that won't help you here: http://www.united.com/page/article/0,6722,51594,00.html

Carry the Pin onboard - should be OK.