I believe your question pertains to casual employment directly conducted by the employer without any intermediary, such as a contractor. Therefore, I prefer to exclude the scenario of the permanency of contract labor in my response.
Understanding Casual Employment
First and foremost, it is crucial to analyze the definition of casual employment. Even the Model Standing Orders listed in Schedule I of the Industrial Employment (Standing Orders) Act, 1946, simply define a casual workman as a workman whose employment is of a casual nature—that's all. To the best of my knowledge and belief, the nature of the work for which a person is employed or engaged and the method of payment are the determining factors in this regard. The nature of work is relative to the principal or main activity of the establishment or the employer. Any work that is incidental and required to be performed intermittently alone can be categorized as casual work. Thus, the irregularity of the work dictates the method of payment for such workers on a daily, hourly, or piece-rate basis, depending on the convenience of quantifying the work done by them monetarily. In essence, it is not the mode of payment, i.e., the frequency at which wages are disbursed or simply put, the wage period, but the method of payment.
Transitioning Casual Workmen to Permanent Status
Regarding the issue of transitioning casual workmen into permanent workmen, I don't believe the Standing Orders of any establishment would be of much assistance as they typically classify workmen based on the nature of their work or purpose of engagement. Even in cases where a special enactment on the subject of employment permanency, such as the Tamil Nadu Industrial Establishment (Conferment of Permanent Status to Workmen) Act, 1981, is in effect, if I am correct, the term "permanent status" has not been clearly defined.
Conclusion
In conclusion, since the nature of a specific work is a matter of fact, the questions of converting casual workmen into permanent workmen of the establishment and the timeframe within which it should be done cannot be definitively answered. However, it is essential to remember that item no. 10 of Part 1 of the Fifth Schedule to the Industrial Disputes Act, 1947, explicitly states that employing workmen as 'badlis,' casuals, or temporaries and retaining them as such for years with the intent of depriving them of the status and privileges of permanent workmen constitutes an unfair labor practice on the part of employers.
Regards