Suwan, You will need the following mandatory documents for tendering.

1) Business Permit City council
2) Vat anf PIn certifictes from KRA
3) Tax Compliant Certificae KRA _ doesnt matter how long you have been in business you must apply for this one an d get it.
4) Business Bank Account
5) Anser several quetions on Business Quatinair: this one is about owners of busiess, share hldings, business locations etc etc aout 15 quuastions are here.
6) Audited accounts minimum 2 years some companies will ask for 3 years, also dpend on whih type and size(cost) of tender the higher the amount the more details will be reiwored, point is to ensure that you have enough capital to deliver and that you have a competent an stanble company.

Please not the above are mandatory again there ar varios mandatory reuirements depending on your economic sector, eg roads, comouters, food etc etc Good luck.