What do you think of issuing warning letters to the employees when they go wrong will make them efficient or discouraged?

I agree with Mr Fazlur Rahman...

The critical point here is deciding when an employee has gone wrong and by how much? If it is only a small mistake counselling would be better. But if there is a serious deviation from the company policy and if it is likely that such behavior in future will cause damage to the organization, then issuing a warning letter to correct the attitude or work culture of the employee becomes essential.

This is a very important issue. Anything went wrong with an employee is to be discussed first face to face with the employee. The manager shall listen carefully and will ask probing question softly to have more information. Thereafter, the Manager shall advise the employee verbally what went wrong and what to be done in similar cases in future and keep a record of the case in file (detail discussion and advice to the employee). It is not advisable to go for warning letter in the first instance. If the similar issues are repeated again, the matter is to be discussed again with the employee and the whole issue is to be forwarded to the HR for further action. In all such cases, the supervising manager must keep the HR manager involved. The HR manager then may call the employee and take corrective action as necessary. The main emphasis to to make the whole process transparent and fair.

discouraged if the didn't get thanks letter and gift when they do the best for work

Thanks

Totally agree with smart answer given by colleague Ahmed Mohammad

i believe that appreciation is a hallmark to get superior performance. Honestly, warning letters to non tolerance activist is another type of appreciation of those who do not take part of such forbidden activities. it publishes corporate compliance culture and help each other to obey all rules and regulation of the company.

Secondly, mutual consultation, counselling and supervisor support may help deserving or disturbing employees to get satisfaction with his/her job and show their commitment and support toward the organization goals. Caring attitude and honest approach are important for employee job satisfaction as oxygen and water needed for life continuity.  

Read:

https://www.template.net/business/hr-templates/warning-letter-template/