The funeral began with Buddhist bathing rituals and will be followed by recitation ceremonies over seven days.
The Leicester City players are due to fly out to Thailand for the funeral after their game against Cardiff later.
Thai billionaire Mr Vichai died along with two members of his staff, the pilot and a passenger when the helicopter came down in a car park moments after taking off from the King Power Stadium on 27 October.
A bathing rite ceremony has started which will be followed by the beginning of the recitation ceremonies.
Jonathan Head, the BBC's South East Asia correspondent, is at the temple and said the ceremony was being held behind closed doors.
There was no definitive start to the ceremony, he said, but close friends and relatives would arrive over the next few hours.
Mr Head said elements of status at the funeral were very important.
"You will see during the funeral artefacts given by King Vajiralongkorn - a special funeral urn and also a five-tiered umbrella that is very high status - being used," he said.
He added: "People will watch the funeral in many ways to see how well thought of Vichai was.
"He was a successful businessman, but sometimes controversial."
Mr Vichai's body arrived in Thailand on Friday ahead of the funeral.
Nusara Suknamai, Kaveporn Punpare, pilot Eric Swaffer and his partner, Izabela Roza Lechowicz, also died in the crash last Saturday. AGENCIES