Mr Hek, along with three other MLAs, will be officially inducted into the saffron party at a rally at the Golf Links ground tomorrow, state BJP president Shibun Lyngdoh told PTI.
The development came days after five Congress MLAs, including former deputy chief minister Rowell Lyngdoh, resigned from the Assembly and announced that they would join the National People's Party (NPP), an ally of the BJP in the NDA, on January 4.
Along with them, three other legislators -- one from the UDF and two Independents -- have also decided to cross over to the NPP, headed by Conrad K Sangma, the son of former Lok Sabha speaker PA Sangma.
"I will put in my resignation, before joining the BJP in the afternoon (tomorrow), along with my friends," Mr Hek told PTI.
He added that the decision to join the saffron party was taken after a thorough consultation with his supporters, friends and family members.
The former state health minister said he was more inclined towards the BJP because of its "sabka saath sabka vikas" agenda and anti-corruption stand.
Mr Hek joining the BJP will be his "home-coming" as he had left the saffron party and joined the Congress in 2009. He was a state minister until last year.
The other MLAs to join the BJP, along with Mr Hek, are -- Nationalist Congress Party's (NCP) Sanbor Shullai and Independents Justine Dkhar and Robinus Syngkon, another leader of the saffron party said on the condition of anonymity. Phone calls to the MLAs for a comment went unanswered.
The decision of the Congress legislators to defect ahead of the Assembly polls in the north-eastern state, where the term of the present House is scheduled to come to an end on March 6, does not augur well for the Rahul Gandhi-led party, which is facing a tough challenge to hold its fort.
At the same time, their decision to join the NPP and the BJP shows that the non-Congress forces are gaining ground in Meghalaya, ahead of the elections.
Bogged by the flight of the MLAs in the poll-bound state, Congress president Rahul Gandhi had, on Saturday last, appointed Celestine Lyngdoh as the new chief of the party's Meghalaya unit, replacing DD Lapang, who was made an adviser to the state unit.
Mr Lyngdoh is a minister in Chief Minister Mukul Sangma's cabinet.
Rahul Gandhi had also appointed Vincent H Pala as the working president of the Meghalaya Pradesh Congress Committee. Mr Hek's decision to quit the Congress will leave the ruling party with 23 legislators, from 30 originally, in the 60-member Meghalaya Assembly.