We study analytically the change in the wealth (x) distribution P (x) against saving propensity λ in a closed economy, using the Kinetic theory. We estimate the Gini (g) and Kolkata (k) indices by deriving (using P (x)) the Lorenz function L(f ), giving the cumulative fraction L of wealth possessed by fraction f of the people ordered in ascending order of wealth. First, using the exact result for P (x) when λ = 0 we derive L(f ), and from there the index values g and k. We then proceed with an approximate Gamma distribution form, Pn(x), of P (x) for non-zero values of λ (n(λ) > 1 for λ > 0 and n(λ) − → ∞ for λ − → 1). Then we derive the results for g and k at λ = 0.25 and as λ − → 1. We note that for λ − → 1 the wealth distribution, P (x) becomes a Dirac δ-function. Using this and assuming that form for larger values of λ (= 1 − , 0 < << 1) we proceed for an approximate estimate for P (x) centered around the most probable wealth (a function of λ), and utilize that for evaluating the L(f ) to estimate in the end g(λ) and k(λ) for large λ values. These analytical results for g and k at different λ are compared with numerical results from the study of the Chakraborti-Chakrabarti model using the Kinetic exchange theory. From the analytical expressions of g and k, we proceed for a thermodynamic mapping to show that the former corresponds to entropy and the latter corresponds to the inverse temperature.