In the present paper we use a simple optical model to describe multi-transverse mode operation of alkali lasers. The model is based on calculations of the pump and laser beam intensities in the gain medium, where the laser beam intensity is a linear combination of the azimuthally-symmetric Laguerre-Gaussian modes. The model was applied to optically pumped cesium vapor laser studied experimentally and theoretically previously [Cohen, T., Lebiush, E., Auslender, I., Barmashenko B.D., and Rosenwaks, S., Opt. Exp. 24, 14374 (2016)]. It was found in our calculations that for low pump power and small pump beam radii, only fundamental lasing mode oscillates, just as shown experimentally in this study. However, for higher pump powers and larger pump beam diameters, several transverse modes participate in oscillation. The number and intensities of the oscillating modes as a function of the pump beam power and radius are found. In order to check the validity of the model, it was applied to pulsed static Cs DPAL [Zhdanov, B. et al, Electron. Lett. 44, 582(2008)] with the pump beam radius much larger than that of the fundamental laser mode and constant gas temperature. The model predicts linear dependence of the laser power on the pump power, the values of the former being in agreement with the experimental results.