According to police, the 28-year-old pop singer initially refused to blow into a breathalyzer and told a traffic police officer that she "is a celebrity and knows many senior police officials".
Giftza, who was with her female friend, refused to leave the vehicle.
Later, another car arrived at the checkpoint. Two men emerged from the vehicle and criticised the officer and the press who had gathered. They were believed to be Giftza's friends.
She then got out of the driver's seat and moved to rest inside her friend's car.
The pop singer later emerged to talk to the press and police, and admitted that she had been drinking alcohol at an entertainment venue in Thong Lor from 10pm Monday to 1am Tuesday.
She told reporters, while still drinking a lot of water, that she wanted to be sober before blowing into the breath tester because she did not want to appear in court.
"He (the officer) told me to blow into the machine, but I feel that I'm not in an appropriate condition," Giftza told reporters. "And when I'm sober, I'll blow into it."
When a reporter asked her to give a breath sample, she said with a faint smile that she would need to drink three bottles of water first.
"I know (that drunk driving is illegal) but I personally feel that I'm not that drunk," she told reporters.
She said she drank only three glasses of alcohol and intended to take a short rest when her car arrived at the checkpoint.
Giftza denied that she contacted a "high-ranking police official" to help her, as claimed by the traffic policeman.
According to the officer, Giftza handed him her phone saying that he could talk to the "high-ranking official". The officer said he did not feel pressured because he was only doing his duty.
She later gave a breath sample after the police officer insisted that she must do as the law requires.
The breathalyser test showed that her breath alcohol level was .082, exceeding the legal .05 limit for driving a vehicle, police said.
Police said Giftza was released on 20,000 baht bail and will be summonsed to appear at Khlon Ton police station at 8.30am Wednesday before the case is forwarded to Phra Khanong Provincial Court.