A per the rules laid down by the bar Council of India, under section VII Rule 51: An Advocate shall not be a full-time salaried employee of any person, Government, firm,corporation or concern, so long as he continues to practise and shall not on taking up such employment intimate the facts to the Bar Council on whose roll his name appears, and shall thereupon cease to practise as an Advocate so long as he continues in such employment.
Nothing in this rule shall apply to a Law Officer of the Central Government or the state government of a State or of any Public Corporation or body constituted by statue who is entitled to be enrolled under the rules of his State bar Council made under Section 28(2)(d) read with section 24(1) of the Act despite his being a full time salaried employee.
Thus you need not surrender your sanad but you have to intimate your Bar Council regarding your employment.