The employer has the right of refusal to pay the salary to the unfaithful employee, who fakes a wrong reason to join another company. The employee is not guarded by the offer letter, since not issued, so he need not serve any notice period and he cannot be sued for leaving with a short notice or goes absconding and join another company, for better prospects.
However, since there is no contract between the employer and employee, even the employer isn't guarded with the offer letter, being not issued. Even he can refuse to pay the salary to the employee, being absconding, or lying a reason of leaving, or leaving with a very short notice and joining another company with better prospects since the employee has put the employer in the peril of possible loss due to sudden absence and non reporting on duty, or leaving at a short notice, not giving enough time or chance to the employer to look out for a replacement. The employee is guilty of knowingly causing disruption in business and absconding for selfish reasons, hence can forfiet his salary for such deceit.