Singh sent a letter of greeting to Tobgay on Saturday night soon after the PDP, the opposition party in Bhutan, won the elections to the Nation Assembly.
Singh said he has already given instruction to officials for preparing the roadmap for Plan assistance to Bhutan and that he look forward to working with Togbay to further enhance the cooperation between the two countries.
Singh invited Tobgay to visit India at an early date.
"It gives me the great pleasure to felicitate Your Excellency on the success of the People's Democratic Party as well as on your own election to the National Assembly on the historic democratic elections in Bhutan," Singh said in the letter.
Assuring him the "steadfast" and "unflinching" support of Indians for the steady steps that Bhutan is taking to further strengthen democratic process and institutions, Prime Minster said, "India is a privileged partner of Bhutan and its people in their socio-economic progress and development."
Singh underlined India's undiminished commitment to Bhutan in preserving the unique and special traditional ties.
"Our bilateral ties are anchored in a strong foundation of trust, mutual confidence and understanding. India is and will remain sensitive to Bhutan and its interests," Singh said.
Singh noted India-Bhutan ties have been carefully nurtured and fostered over many decades with the guidance and vision of Their Majesties the Druk Gyalpos of Bhutan and the constructive cooperation of the governments of two countries.
“Our endeavour would be to strengthen these ties further."
"We look forward to working with you and your colleagues to further enhance our cooperation for the benefit of the people of both our countries. I have, therefore, already
instructed officials of my government to prepare for the discussions on our Plan assistance to Bhutan," he said.