Pol Lt Pattarawut Siripru, a duty officer at Muang Ubon Ratchathani police station, said a group of five armed people wearing knitted hats over their faces broke into the gold shop as it was about to be opened by three staff at 6am.
They handcuffed the staff and forced them to disclose the shop's safe code.
After taking 1,500-baht-weight of gold bars and ornaments, valued at more than 31.5 million baht, and 1.5 million baht in cash from the safe, one of the suspects tampered with the shop's closed circuit television (CCTV) cameras to destroy evidence of the crime.
The armed suspects threatened staff, warning them not to call the police, before taking off on motorcycles.
Police later arrested one of the suspects, Sarawut Ketkul, who allegedly confessed that he gave the stolen 1.5 million baht to his girlfriend, Orachorn Kongmalai.
The suspect's girlfriend was arrested in front of a restaurant and the stolen money was recovered.
Police were able to get the names of the other accomplices and were tracking them down.
In Nakhon Ratchasima, police arrested two women accused of selling fake gold bars to local shops on Wednesday.
Pol Lt Col Thaworn Laopho, an investigator at Muang Nakhon Ratchasima police station, said the two suspects are sisters - Woranut Kanto, 44, and Siriporn Jitratikornkul, 41.
They were accused of selling four gold bars weighing four kilogrammes in total to two gold shops in Muang district for five million baht.
After the sale, the gold dealers heated the gold bars to melting point to see if they were real. They then discovered that the gold bars were counterfeit.
The two suspects allegedly told investigators that they bought the gold bars from another gold shop in Nakhon Ratchasima and were not aware that they were fake. But investigators did not believe them and charged them with fraud.
Suthep Nattakarnkanok, one of the gold dealers who was tricked by the two women, said the fake gold bars looked and felt very real, and were coated with about five-baht-weight of gold.
"If you didn't burn the gold bars at 3,000 degrees, you would not know that they were 'stuffed'," Mr Suthep said.
Chaichana Prapruetthipong, president of a gold traders' club in Nakhon Ratchasima, said the fake gold bars were likely to have been produced abroad. Gold dealers nationwide should be more careful when buying gold bars, he added.