Add boundary (shp) borders in levelplot

Question

So, I have a problem with levelplot function. I have peatlands.shp, and study area .shp. And I wanna put it down into my levelplot() function that appear border (administration lines/peatlands/land type)

library(RColorBrewer)
levelplot(
  clmon_obs,
  pretty = TRUE,
  names.attr = month.abb,
  layout = c(4, 3),
  at = seq(0, 600, 100),
  col.regions = brewer.pal(8, "Blues"),
  ylab = list("Latitude", cex.lab = 1.2, fontlab = 2, col.lab = "black"),
  xlab = "",
  cex.names = 0.8,
  colorkey = list(
    space = "right",
    labels = list(
      at = seq(0, 600, 200),
      labels = seq(0, 600, 200),
      cex = 0.8
    ),
    title = list("values", rot = 0, cex = 0.8, font = 1, col = "black")
  ),
  par.settings = list(
    axis.line = list(col = "black", lwd = 0.8),
    strip.background = list(col = "lightgray"),
    strip.shingle = list(col = "transparent"),
    strip.border = list(col = "black", lwd = 0.8),
    add.text = list(col = "black", font = 1, cex = 1),
    layout.heights = list(bottom.padding = 5)
  ),
  panel = function(...) {
    panel.levelplot(...)
    region = TRUE
    contour = FALSE
    region.type = c("grid", "contour")
    panel.grid(h = 4, v = 4, col = "black", lty = 2, lwd = 0.4)
  }
)