
Jittapas said she apologised and would resign as a staff of the PM's secretary team headed by Panithan Wattanayakorn, deputy PM's secretary general and acting government spokesman.
The 23-year-old heiress to Singha Beer fortune was seen handing out the controversial calendars from her BMW's trunk to officials, security guards and newsmen who queued up to take them on Wednesday.
In her letter of resignation, she said she did not intend to distribute the calendars. "I bring along the calendars because some friends want to have them," she said.
Many reporters saw the calendars wanted them. "So, I gave them to everyone. I admitted that I did not think that this would turn out to be big deal. This happened because of my recklessness," she said.
"I am upset that the incident affected not only my family and I but also many senior people whom I respect. I myself will take full responsibility for this by resigning from position in PM's Secretariat," she said.
The resignation would take effective on Thursday.
She will take this as a lesson and hope that politics will give her another opportunity in the future.
The calendars with models body-painted which have brand name and logo of an alcohol drink produced by Singha's daughter company have become controversial as its producing and distribution were considered violating laws.
Dr Saman Futrakul, director of the Alcohol Beverage and Tobacco Consumption Control Committee, affirmed that the selling of such sexy calendars, rather than giving them away for free, remained a violation of the law.
He said the selling or distribution of calendars with models body-painted to emphasise the alcohol drink's brand name or logo was a form of advertising via print media.
Supermodel Methinee Kingpayom, who produced the calendar, has said she would start selling the 2010 calendar in one to two days.
But Saman said they would proceed with legal action against the sellers on grounds the calendar was an illegal item, so selling or contributing to it was illegal.
He had earlier warned that, under the Alcoholic Beverage Control Act, distributing a calendar with a brand name or logo but no worthy information could bring a one-year jail term and/or Bt50,000 fine, as well as a daily fine of Bt50,000 until a correction was made.