áÍ´ÁÔ¹¤ÃѺÁÕä¿Åì PDF ¢Í§¹ÔÂÒÂàÃ×èͧ¹ÕéÃÖ»ÅèÒǤÃѺ element online ÁËÒàÇ·Í͹äŹì ÍÅàǧ 3.1 - 5.2 ¢Íº¤Ø³¤ÃѺ